Concentration profiles of low-index surfaces of PtCo alloys: application of an improved thermodynamic theory

L.Z. Mezey^* and W. Hofer

Surf. Sci. 352-354 (1996) 15-20

Several years ago a general theory of solid surfaces was developed by one of us (MTCIP: Modern Thermodynamic Calculation of Interface Properties). A part of it describes the surface concentration profile of the thermodynamic equilibrium state by a system of coupled, non-linear equations. This system was solved in a first approximation for dilute binary mixtures and applied to several bimetallic alloys, with reliable results in several publications, even in the case of surface interactions with environmental (oxygen) atoms. Recently a much more detailed second approximation (MTCIP-2A) has been developed (under publication now). It has been shown to give good agreement with experimental concentration profiles for the three low-index surfaces of PtNi for all the bulk concentrations investigated experimentally (for T=1120K). Here the MTCIP-2A is shortly outlined and applied to obtain concentration profiles for Pt₂₅Co₇₅(110), Pt₂₅Co₇₅(111) and Pt₈₀Co₂₀(111) surfaces (for T=1120K). These results, too, are in agreement with recent LEED experiments for all the surface layers investigated. To our knowledge, these are the first calculated concentration profiles for PtCo.

Corresponding author: W. Hofer (hofer)